Universal valve annulus sizing device

ABSTRACT

A device for measuring an internal dimension of a native cardiac valve annulus includes an elongated support member having a proximal portion and a distal portion. A measuring portion is coupled to the distal portion, and an indicator is coupled to the proximal portion of the support member. The measuring portion is biased towards a deployed configuration such that when deployed it applies an outwardly directed radial force to the native valve annulus.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.14/222,598, filed Mar. 22, 2014, which is a continuation of U.S.application Ser. No. 12/727,098, filed Mar. 18, 2010, now U.S. Pat. No.8,715,207, which claims the benefit of provisional application No.61/161,462, filed Mar. 19, 2009, entitled “UNIVERSAL VALVE ANNULUSSIZING DEVICE,” which is herein incorporated by reference in itsentirety.

TECHNICAL FIELD

The present invention relates to devices and methods for measuring thesize of an anatomical valve annulus, and more particularly, to devicesfor use in measuring the size of a cardiac valve annulus in conjunctionwith implantation of an expandable prosthetic heart valve.

BACKGROUND

Various sutureless heart valve prostheses have been considered forreplacing diseased or defective native cardiac valves (e.g., the aorticvalve). One such type of prosthetic heart valve includes a radiallycollapsible/expandable stent, which supports a set of valve leaflets.Typically, the stent is radially contracted during implantation of theprosthetic valve at the desired location. To optimize performance, thestent is sized such that, if unrestrained, it can expand to a diametersomewhat greater than the diameter of the annulus of the valve to bereplaced and/or the vessel proximate to the native valve (i.e., in thecase of an aortic valve prosthesis, the ascending aorta).

To ensure proper anchoring and operation of the prosthetic valve insitu, it is helpful to assess the size of the patient's anatomical valveannulus. The annulus includes dense, fibrous rings attached to theadjacent atrial or ventricular muscle fibers. In some valve replacementprocedures, the physician excises the defective native valve leaflets toprepare the annulus for implantation of the replacement valve.Typically, physicians use a set of sizing obturators, which are providedby various heart valve manufacturers, to obtain an estimate of thediameter of the native valve annulus. These sizing obturators typicallyinclude a cylindrical body having a flat, annular flange thereabout. Thephysician typically advances the flange to a location adjacent thesuperior aspect of the valve annulus, but does not typically advance theflange to an intra-annular position. This process may require thephysician to repeatedly introduce various sizing obturators to the valveannulus to obtain this size estimate. This procedure requires much timeand effort and offers minimal accuracy. This procedure also reliessignificantly on the skill of the implanting physician, as proper sizingis largely based upon the skill and technique of the physician.

SUMMARY

The present invention, according to exemplary embodiments, is a devicefor measuring an internal dimension of a native cardiac valve annulus.The device includes an elongated support member having a proximalportion and a distal portion including an end having a bore and alongitudinal slot, a measuring band having a first end and a second end,the first end disposed within the bore and the second end coupled to thedistal portion, a shaft extending through the support member, the shafthaving a distal end coupled to the first end of the measuring band and aproximal end, and an indicator coupled to the proximal end of the shaft,the indicator adapted to provide an indication of the internaldimension. The measuring band has a contracted configuration in whichthe band is at least partially wound about a transverse axis and anexpanded configuration in which the band is substantially unwound.

The present invention, according to other embodiments, is a device formeasuring an internal dimension of a native cardiac valve annulus, thedevice comprising a body portion and a measuring portion, the measuringportion including an expandable element configured to substantiallyadapt to the shape of the annulus.

The present invention, according to other embodiments, is a method ofimplanting an expandable prosthetic valve at a native valve annulus. Themethod includes removing a native valve leaflet, debriding the nativevalve annulus, stressing the valve annulus by applying a force similarto that applied by a prosthetic valve, obtaining an estimate of theperimeter of the valve annulus, selecting an appropriate prostheticvalve based on the estimate, and implanting the appropriate prostheticvalve at the native valve annulus.

The present invention, according to another embodiment is a method ofimplanting an expandable prosthetic valve at a native valve annulus. Themethod includes removing a native valve leaflet, debriding the nativevalve annulus, stressing the valve annulus by applying a force similarto that applied by a prosthetic valve, obtaining an estimate of theperimeter of the valve annulus, selecting an appropriate prostheticvalve based on the estimate, and implanting the appropriate prostheticvalve at the native valve annulus.

Another embodiment of the present invention is a kit for implanting asutureless prosthetic heart valve, the kit comprising a sizing tool formeasuring an internal dimension of a native cardiac valve annulus, thesizing tool comprising an expandable element configured to substantiallyadapt to the shape of the annulus, and an expandable, stented prostheticheart valve. The prosthetic heart valve, in some embodiments, generatesa first radial force against the valve annulus upon implantation and theexpandable element generates a second radial force, the second radialforce differs from the first radial force by less than about 10%.

While multiple embodiments are disclosed, still other embodiments of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the invention. Accordingly, the drawings anddetailed description are to be regarded as illustrative in nature andnot restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective partial cut-away view of a valve sizer in adeployed state according to one embodiment of the present invention.

FIGS. 2A-2B are perspective views of the valve sizer of FIG. 1 indeployed and undeployed configurations.

FIGS. 3A-3C are a perspective view, a top plan view and an end planview, respectively, showing the measuring band in a fully extendedconfiguration.

FIGS. 4A-4B are a perspective view and an end plan view of the measuringband in a contracted configuration.

FIGS. 5A-5B are a perspective view and an end plan view of the measuringband in a deployed configuration.

FIGS. 6A-6B are schematic views showing the measuring band in acontracted and a deployed configuration, respectively.

FIG. 7 is a schematic view illustrating a sizing device according toanother embodiment of the present invention.

FIG. 8 is a partial sectional view of the sizing device shown in FIG. 7.

FIG. 9 is a schematic view of an exemplary embodiment of the measuringportion of the sizing device shown in FIG. 7 in deployed and undeployedconfigurations.

FIG. 10 is a flow chart showing a method of sizing a valve annulus,according to an embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 is a perspective partial cut-away view of a valve sizing device10 in a deployed state within a patient's aortic valve annulus 14,according to one embodiment of the present invention. While thefollowing description of the various embodiments of the presentinvention are generally described with reference to an aortic valveannulus, it is also useful for measuring a dimension of other cardiacvalve annuli, including for example the pulmonary valve annulus.Further, the devices of the present invention can be used to measureother valve annuli as well as the inner dimensions of vessels or othertubular anatomical structures.

As is known, and as shown in FIG. 1, the left ventricle 18 is coupled tothe ascending aorta 20. During normal operation, the left ventricle 18pumps blood out of the heart through the aortic valve and into theascending aorta 20. The aortic valve is a semilunar valve including aset of valve leaflets surrounding the aortic annulus 14, which isdefined by the periannular tissue located at the most distal portion ofthe left ventricular outflow tract. The annulus 14 includes dense,fibrous rings attached to the adjacent atrial or ventricular musclefibers. As shown in FIG. 1, the sizing device 10 is positioned to allowmeasurement of a diameter and/or a perimeter of the aortic annulus 14.As shown, access to the annulus 14 is obtained from a superior positionthrough an incision in the ascending aorta 20. In the illustratedembodiments, the native aortic valve leaflets have been removed. It willbe appreciated, however, that removal of the native valve leaflets isnot a requirement of the sutureless aortic valve replacement procedure.That is, in various embodiments, the valve prosthesis can be implantedwithout removing the native valve leaflets.

The sizing device 10 may be used in connection with implantation of anexpandable/contractible replacement heart valve of the type generallyknown in the art. The sizing device 10 may be used, for example, inconnection with any sutureless aortic valve prostheses, for example,including percutaneously delivered aortic valve prostheses. In variousexemplary embodiments, the sizing device 10 is used in connection withimplantation of any of the prosthetic valves disclosed in co-pending andcommonly assigned U.S. patent application Ser. Nos. 11/066,346 and11/352,021, the disclosures of which are incorporated herein byreference in their entireties.

FIGS. 2A-2B are perspective views of the valve sizer of FIG. 1 indeployed and undeployed configurations, respectively. As shown, thesizing device 10 includes a main body portion 24 supporting a measuringportion 28. As shown in FIG. 2A, the measuring portion or band 28 isdisposed in an expanded configuration, in which the measuring band 28has an effective diameter larger than that of the distal end of the mainbody portion 24, while in FIG. 2B, the measuring band 28 is disposed ina collapsed configuration, in which it has an effective diameter aboutequal to that of the distal end of the main body portion 24. Thisexpandable/collapsible design facilitates delivery of the tool usingstandard minimally-invasive delivery techniques and instruments. Thisdesign also provides the device 10 with the ability to measure a widevariety of valve annuli, each having a distinct diameter or perimeterdimension.

As further shown in FIGS. 2A-2B, the main body portion 24 includes anelongated support member 32, which couples an adjustable member or knob34 at its proximal end to an adjustment mechanism 36 at its distal end.In various embodiments, a shaft or coupling rod (not shown) extendsthrough an internal lumen in the elongated support member 32 androtationally couples the adjustable knob 34 to the adjustment mechanism36. In various embodiments, the support member 32 includes a linkage orplurality of linkages, which allow adjustment of the orientation andshape of the handle (e.g., both angularly and rotatably) relative to theadjustable portion 36. In various embodiments, the support member 32 mayinclude a locking mechanism to allow the physician to lock the positionof the support member when desired. In various embodiments, all or aportion of the support member 32 may be made flexible in addition to orin lieu of the inclusion of the linkages, thereby providing alternativeor additional flexibility in orienting the adjustment mechanism 36inside the valve annulus.

According to some embodiments, the device 10 is configured such that theadjustment mechanism 36 responds to movement imparted on the adjustableknob 34. For example, during use, a physician could apply a rotationalforce having a desired magnitude to the adjustable knob 34. This forcein-turn causes a corresponding rotation of the adjustment mechanism 34.This rotation of the adjustment mechanism causes deployment of themeasuring band 28. According to other embodiments, as further explainedbelow, the measuring band 28 is biased to an open or expanded position,such that it self-expands inside the valve annulus, which causesrotation of the adjustment mechanism 36, which in-turn causes rotationof the adjustable knob 34. In some embodiments, the adjustable knob 34or the adjustment mechanism 36 include a latch or lock for retaining themeasuring band in the collapsed configuration. The physician may thenmanipulate this latch or lack at an appropriate time, to allow themeasuring band to deploy or expand.

An annular member 38 is coupled near a proximal end of the elongatedsupport member 32 adjacent the adjustable knob 34. The annular member orindicator 38 includes indicia 40 disposed circumferentially about theannular member. These indicia are configured to indicate a degree ofdeployment of the measuring band 28. In the embodiment of FIGS. 2A and2B, for example, the indicia 40 include various numbers representativeof the diameter of the measuring band in millimeters. In otherembodiments, the indicia 40 are configured to indicate an effectivelength (i.e., the length extending out of the adjustment mechanism 36)of the measuring band. Of course, one skilled in the art, will recognizethat a wide variety of other indicia may be useful in connection with avalve sizing procedure.

FIGS. 3A-3C show various views of the adjustment mechanism 36 located ata distal end of the sizing device 10. In the configuration shown inFIGS. 3A-3C, for purposes of illustration only, the measuring band 28has been partially disassembled from the adjustment mechanism 36. Thesefigures to not show a configuration obtained by the measuring band 28during actual use of the sizing device 10. As shown in FIG. 3A, theadjustment mechanism 36 includes a cylindrical holder 44, the measuringband 28, and a hub portion 45. As shown, the cylindrical holder 44,which has a proximal end 46 and a distal end 48, is structurallyseparate from the elongated support member 32. In such embodiments, theproximal end 46 of the cylindrical holder 44 is adapted to couple to adistal end of the sizing device 10, such as for example by use of aninterference fit with a distal portion of the support member 32.According to other embodiments, the cylindrical holder is an integrallyformed portion of the distal end of the elongated support member 32. Ineither case, the cylindrical holder is fixed both longitudinally androtationally during use of the device.

The cylindrical holder 44 includes an opening or slot 52 extendinglongitudinally through a portion thereof. In some embodiments, the slot52 extends along the entire length of the holder 44 from the proximalend 46 to the distal end 48. Adjacent the slot 52 is a coupling edge 54.As shown, the holder 44 also includes an annular lip 56 located at thedistal end 48. In other embodiments, the holder 44 includes an annularlip at the proximal end 46 as well. The cylindrical holder 44 defines aninternal, central chamber or bore 60.

As shown in FIGS. 3A-3C, the measuring band 28 includes an elongatedportion extending from a proximal end 64 to a distal end 68. Theproximal end 64 is coupled to the holder 44 at or near the coupling edge54. The distal end 68 of the measuring band 28 is coupled to the hubportion 45. As shown, the hub portion 45 includes a protrusion 72defining an internal engagement portion 76. The protrusion 72 andengagement portion 76 facilitation coupling of the hub portion 45 to thecoupling rod, which extends from the adjustment mechanism 36 to theproximal end of the sizing device 10. The measuring band 28 may be madefrom any material having suitable physical characteristics. In variousembodiments, the band 28 is made from a biocompatible polymeric ormetallic material. In embodiments where the band 28 is self-expandable,the band is made from a polymer or metal having shape memory and/orsuperelastic properties. Once such class of superelastic materials wellknown in the art are nickel-titanium alloys, such as nitinol. Accordingto one exemplary embodiment, the measuring band has a length of betweenabout 150 and 190 mm, a height of between about 1 and 10 mm, and athickness of about 0.05 and 2 mm. In other embodiments, the measuringband may include other dimensions as appropriate for use of the ban inmeasuring the circumference of a valve annulus.

In some embodiments, the measuring band 28 includes a longitudinallyextending radiopaque portion to facilitate visualization of themeasuring band during use of the device. In other embodiments, thelongitudinally extending edge (or edges) of the measuring band 28 aretapered or otherwise softened, to help minimize trauma to the valveannulus 14 or adjacent tissue during a sizing procedure.

According to various embodiments the hub portion 45 and the measuringband 28 are removable from the holder 44. In these embodiments, themeasuring band 28 and hub portion 45 of the sizing device 10 are readilydisposable after use, while the remaining portions of the device may besterilized and reused by the physician. In these embodiment, forexample, the measuring band can be removed by unwinding and expandingthe measuring band and then manipulating the measuring band around thedistal annular lip 56. The measuring band 28 and hub 45 can then be sliddistally out of the holder 44 for disposal. A new, sterile measuringband 28 and hub 45 can then be inserted into the holder 44, and theengagement portion 76 coupled to the coupling rod.

FIGS. 4A-4B show the adjustment mechanism 36 in an assembled, collapsedconfiguration. For illustration purposes only, the cylindrical holder 44is shown separated from the elongated support member 32. As shown inFIGS. 4A-4B, the measuring band 28 is wound about the holder 44 in aclockwise direction, such that it extends along an outer surface of theholder 44, extends through the slot 52, and extends along an internalsurface of the holder 44 in the central chamber 60. The proximal end 64of the measuring band 28 is attached at or near the coupling edge of theholder 44, and the distal end 68 of the measuring band is coupled to thehub portion 45. In this configuration, the measuring band has a minimaleffective diameter (D₁), which facilitates access to the valve annulus14 using standard minimally invasive access techniques and instruments.In the embodiment shown, the annular lip 56 extends radially outwardfrom the holder a distance about equal to the thickness of the measuringband 28. In this embodiment, the leading (distal) edge of the measuringband is thus covered or protected by the annular lip 56. As shown inFIGS. 4A-4B, in the assembled configuration, the hub portion 45 islocated inside the central chamber 60, with portions of the measuringband 28 wound thereabout.

FIGS. 5A-5B show the adjustment mechanism 36 in an assembled, expandedconfiguration. Again, for illustration purposes, the cylindrical holder44 is shown separated from the elongated support member 32. As shown, inthe expanded configuration, the measuring band 28 is at least partiallyunwound, which results in an the measuring band 28 defining an expandedeffective diameter (D₂). As shown, the proximal portion 64 of themeasuring band 28 remains attached to the holder 44, and the distalportion 68 remains attached to the hub portion 45. The hub portion 45,however, has rotated in the direction indicated by the arrow in FIG. 5B,to allow the measuring band to extend out through the slot 52 and awayfrom the holder 44. The effective length (i.e., the length extending outfrom the holder 44) corresponds to an amount of rotation of the centralhub 45. As the hub rotates in a counter-clockwise direction, themeasuring band expands outwardly from the holder 44, and as the hubrotates in a clockwise direction, the measuring band contracts towardsthe holder 44. In the most expanded configuration, the hub portion 45remains inside the holder 44, but all or nearly all portions of themeasuring band 28 have extended out through the slot 52.

FIGS. 6A-6B show schematic sectional views of a distal end of the sizingdevice 10, which has been placed at an intra-annular location by theimplanting physician. In the illustrated embodiment, the native valveannulus 14 is not precisely cylindrical in cross section, but insteadhas a slightly trigonal sectional configuration. While the sizing device10 of the present invention is well suited to measure a diameter orperimeter dimension of a cylindrical annulus, it is also well suited tomeasure the effective diameter or perimeter of a non-cylindrical valveannulus. Likewise, the device of the present invention is able tomeasure the perimeter of a valve annulus that includes calcification orother imperfections.

As shown in FIG. 6A, the physician has located the adjustment mechanism36 of the sizing device 10 inside the valve annulus, with the measuringband 28 in a contracted configuration. Next, the physician activates theadjustment mechanism 36 to enable the measuring band 28 to expandradially outward into contact with an internal surface of the valveannulus, as shown in FIG. 6B. According to various embodiments, thematerials and dimensions of the measuring band 28 are selected to enablethe band to readily expand outward and to substantially or entirelyconform to the inner surface of the valve annulus.

According to some embodiments, the measuring band 28 is unwound andexpanded manually by the implanting physician. In these embodiments, thephysician can expand and contract the measuring band by turning theadjustable knob 34. As explained above, the adjustable knob 34 iscoupled (using, for example, a coupling rod) to the adjustment mechanism36. Specifically, in various embodiments, the adjustable knob is coupledto the hub portion 45 of the adjustment mechanism. By turning theadjustable knob 34, the physician can effect a corresponding rotation ofthe hub portion, which in turn will effect an unwinding or unfurling ofthe measuring band 28. In these embodiments, the physician can rotatethe adjustable knob 34 until she feels a certain degree of resistance,which corresponds to an amount of radial force applied by valve annulus14 against the measuring band 28. When the physician determines that shehas caused an appropriate amount of force against the valve annulus, shecan read the indicia 40 on the handle, which indicates the correspondingdiameter or effective length of the measuring band 28.

In some embodiments, the sizing device 10 includes a torque limitingdevice of the type known in the art. This torque limiter is placedbetween the knob 34 and the adjustment mechanism 36 and prevents thephysician from applying an excessive force of a magnitude that couldcause damage to the native valve annulus.

According to other embodiments, the measuring band 28 is made from asuperelastic material, which is biased to the fully expandedconfiguration. In one such exemplary embodiment, the measuring band ismade from a material and has dimensions selected such that the measuringband will expand to a diameter greater than the largest expected valveannulus diameter. In one embodiment, for example, the measuring band 28is biased to an expanded configuration (such as that shown in FIG. 5A)having an effective diameter of greater than about 26 mm. In theseembodiments, the material and dimensions of the measuring band 28 arealso selected such that the measuring band generates an outward radialforce against the inward-facing surface of the valve annulus 14, whichradial force approximates that radial force generated by theself-expandable prosthetic valve to be implanted in the valve annulus14. In some embodiments, the radial force generates by the measuringband 28 differs from the radial force generated by the prosthetic heartvalve by not more than 10 percent. In other embodiments, the radialforces differ by not more than 5 percent. In still other embodiments,the radial forces differ by not more than 2 percent.

As will be apparent to the skilled artisan, by setting theself-expanding radial force of the measuring band 28 approximately equalto the radial force generated by the prosthetic valve to be implanted,the sizing device 10 may obtain a more accurate measure of the internaldimensions of the valve annulus upon implantation of the prostheticvalve. The implantation of a self-expanding prosthetic valve may resultin a change in shape and/or size of the valve annulus 14, which changeswill be detected by the sizing device 10 of the present invention. Inthese embodiments, the implanting physician allows the measuring band toexpand inside the valve annulus and then reads the correspondingdimensional information from the indicia 40 disposed on the annularmember 38.

According to various embodiments, the measuring band 28 is sufficientlyflexible to allow it to substantially conform to the internal surface ofthe valve annulus 14. In some embodiments, for example, the measuringband 28 is able to readily take on a radius of curvature of less thanabout 2 mm. This flexibility allows the measuring band to substantiallyconform to valve annuli having irregular shapes.

FIG. 7 is a schematic view illustrating a sizing device 100 according toanother embodiment of the present invention. As shown in FIG. 7, thedevice 100 includes a main body portion 104 and a measuring portion 108.The device 100 is shown in one possible operating configuration with themain body portion or handle 104 extending through a vessel downstreamfrom the valve and the measuring portion located generally insider thevalve annulus. In FIG. 7, the measuring portion 108 is shown in adeployed or expanded configuration, such that the measuring portion 108is in contact with an inner wall or surface of the valve annulus.

FIG. 8 shows a partial sectional view of the sizing device 100. Asshown, the main body portion includes an elongated support member 110,which couples an adjustable member 112 to the measuring portion 108. Asfurther shown in FIG. 8, the main body portion houses or contains atorque member or rod 116, which is coupled to the adjustable member 112at a proximal end and includes a threaded distal end 118. The threads ofthe rod 116 engage corresponding threads of a tapered element 122, suchthat a rotation applied to the adjustable member 112 causes rotation ofthe rod 116, which in turn causes longitudinal motion of the taperedelement 122 with respect to the main body portion 104. As the taperedelement is moved towards the main body portion 104, it slides along aninterior surface of the measuring portion 108, which in turn causes themeasuring portion to expand outwardly. Accordingly, a user of the device100 can apply a torque to the adjustable member 112 to cause expansionor deployment of the measuring portion 108, until the measuring portioncontacts the interior surface of the annulus. In some embodiments, theadjustable member includes an associates scale which is configured toindicate the corresponding diameter or circumference of the measuringportion 108.

According to other embodiments, the measuring portion 108 isself-expanding. In some such embodiments, the measuring portion 108 isexpanded in an unbiased position, such that it defines an overalldiameter that is slightly larger than a diameter of the target valveannulus. In exemplary embodiments, the measuring portion 108 is madefrom a polymer or metal having shape memory and/or superelasticproperties. Once such class of superelastic materials well known in theart are nickel-titanium alloys, such as nitinol. In some embodiments,the measuring portion is held in a collapsed or compressed configurationby a sheath or tube disposed over the elongated support member 110. Themeasuring portion 108 is then deployed (i.e., allowed to self-expand) byretracting the sheath and allowing the measuring portion to expandradially into contact with an inner surface of a valve annulus. In suchembodiments, the elongated support member may include indicia which aredisposed axially along the shaft such that the indicia correspond to adiameter or circumference of the measuring portion 108. In this fashion,the indicia will provide the user with an indication of the diameter orcircumference of the target valve annulus.

FIG. 9 shows a schematic view of an exemplary embodiment of themeasuring portion 108. As shown in FIG. 9, in this embodiment, themeasuring portion includes a plurality of measuring elements or petals120A to 120F. In various exemplary embodiments, the measuring portion108 may include more or fewer petals 120, as appropriate for measuringthe desired valve annulus. As shown in FIG. 9, the petals 120 areexpandable (as described above) from a collapsed configuration to andexpanded configuration. An exemplary expanded configuration is shown bythe elements or petals marked 120A′ to 120F′.

FIG. 10 is a flowchart illustrating one exemplary technique 200 forusing the sizing device 10 or 100 of the present invention. As shown inFIG. 7, in some embodiments, the physician first removes the nativeanatomical valve leaflets from the valve (block 210). The physicianthen, in some embodiments, debrides or otherwise smoothes out the tissueat the valve annulus (block 220). The physician then introduces thesizing device 10 of the present invention to an intra-annular locationand activates or releases the measuring band until it applies anoutwardly directed force similar to that applied by the prosthetic valveto be implanted (block 230). While this force is being applied to thevalve annulus, the physician reads an estimate of the annulus diameteror perimeter from the device (block 240). Based on this estimate of theannulus dimension, the physician selects an appropriately sizedprosthetic valve (block 250). The physician then implants theappropriately sized valve at the native valve annulus (block 260).

Various modifications and additions can be made to the exemplaryembodiments discussed without departing from the scope of the presentinvention. Accordingly, the scope of the present invention is intendedto embrace all such alternatives, modifications, and variations as fallwithin the scope of the claims, together with all equivalents thereof.

We claim:
 1. A device for measuring an internal dimension of a nativecardiac valve annulus, the device comprising: an elongated supportmember having a proximal portion and a distal portion and a longitudinalaxis; a holder coupled to the distal portion and having an inner borethat extends along the longitudinal axis of the elongated supportmember; a hub disposed within the inner bore; a measuring band having afirst end attached to the holder and a second end attached to the hub;an indicator coupled to the proximal portion; and a torque applicatorcoupled to the proximal portion; and an adjustable knob coupled to theproximal portion, wherein the measuring band has a contractedconfiguration in which the measuring band is at least partially woundabout the hub to have a contracted diameter equal to or less than a borediameter of an access instrument, and wherein a rotational force appliedto the torque applicator and the adjustable knob causes deployment ofthe measuring band, such that the measuring band expands to form a loopwith the holder situated inside the loop and the indicator indicates adegree of deployment of the measuring band.
 2. The device of claim 1,wherein the measuring band is removable from the distal portion of theelongated support member.
 3. The device of claim 1, wherein the torqueapplicator and the adjustable knob includes a torque limiter configuredto restrict the amount of torque transmitted to the measuring band. 4.The device of claim 1, wherein the elongated support member includes alinkage that allows adjustment of the orientation and a shape of ahandle of the device, and wherein the elongated support member includesa locking mechanism to lock a position of the elongated support member.5. The device of claim 1, further comprising a minimally invasive accessinstrument and wherein the measuring band is configured to be advancedthrough the minimally invasive access instrument in the contractedconfiguration.
 6. The device of claim 1, wherein the measuring band isconfigured to generate an outwardly directed radial force against thenative cardiac valve annulus and dimensions of the measuring band areselected such that the outwardly directed radial force has a magnitudeabout equal to that of a self-expanding prosthetic valve to beimplanted.
 7. The device of claim 1, wherein the measuring band has anexpanded configuration in which the measuring band is unwound and has aneffective diameter larger than that of the holder.
 8. A device formeasuring an internal dimension of a native cardiac valve annulus, thedevice comprising: an elongated support member having a proximal portionand a distal portion and a longitudinal axis; a holder coupled to thedistal portion and having an inner bore that extends along thelongitudinal axis of the elongated support member; a hub disposed withinthe inner bore; a measuring band having a first end coupled to theholder and a second end coupled to the hub; and at least one of a torqueapplicators and an adjustable knob coupled to the proximal portion,wherein the measuring band has a contracted configuration in which aportion of the measuring band is wound about the hub and disposed withinthe inner bore of the holder and the measuring band has a contracteddiameter equal to or less than a bore diameter of an access instrument,and wherein a rotational force applied to the at least one of the torqueapplicator and the adjustable knob causes deployment of the measuringband, such that the measuring band expands within the annulus to form aloop with the holder situated inside the loop.
 9. The device of claim 8,wherein the measuring band is removable from the distal portion of theelongated support member.
 10. The device of claim 8, wherein the atleast one of the torque applicator and the adjustable knob includes atorque limiter configured to restrict the amount of torque transmittedto the measuring band.
 11. The device of claim 8, wherein the elongatedsupport member includes at least one linkage that allows adjustment ofan orientation and a shape of a handle of the device, and wherein theelongated support member includes a locking mechanism to lock a positionof the elongated support member.
 12. The device of claim 8, wherein theadjustable knob includes a locking mechanism to lock the measuring bandin a desired configuration.
 13. The device of claim 8, furthercomprising a minimally invasive access instrument and wherein themeasuring band is configured to be advanced through the minimallyinvasive access instrument in the contracted configuration.
 14. A devicefor measuring an internal dimension of a native cardiac valve annulus,the device comprising: an elongated support member having a proximalportion and a distal portion and a longitudinal axis; a holder coupledto the distal portion and having an inner bore that extends along thelongitudinal axis of the elongated support member; a hub disposed withinthe inner bore; a measuring band having a first end coupled to theholder and a second end coupled to the hub, an indicator coupled to theproximal portion; a torque applicator or an adjustable knob coupled tothe proximal portion; wherein the measuring band has a contractedconfiguration in which the measuring band is at least partially woundabout the hub to have a contracted diameter equal to or less than a borediameter of an access instrument, wherein a rotational force applied tothe torque applicator or adjustable knob causes deployment of themeasuring band, such that the measuring band expands to form a loop withthe holder situated inside the loop.
 15. The device of claim 14, furthercomprising a minimally invasive access instrument and wherein themeasuring band is configured to be advanced through the minimallyinvasive access instrument in the contracted configuration.